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Abstract:

A composite is provided that has a structured sol-gel layer on a
substrate. The sol-gel layer is extremely resistant against mechanical
stress and other influences from outside due to its production method.
The composite is suitable for use in a lot of technical fields, since the
sol-gel layer can be provided with nearly any arbitrary structure. For
example, the structure may result in optical effects and may be used in
optical systems.

Claims:

1. A composite comprising: a substrate; and a structured sol-gel layer,
wherein the structured sol-gel layer has a modulus of elasticity of 200
to 10,000 N/mm2 and comprises a reaction product of at least one
alkoxysilane with at least one polysiloxane, wherein the at least one
polysiloxane has a mean molecular weight of at least 1,500 and at most
300,000 g/mol.

2. The composite according to claim 1, wherein the substrate is a
material selected from the group consisting of glass ceramic, glass,
ceramic, and a polymer plastic.

3. The composite according to claim 1, wherein the structured sol-gel
layer is a stamped layer.

4. The composite according to claim 3, wherein the stamped layer
comprises a structure with a depth of 2 μm to 200 μm.

5. The composite according to claim 1, wherein the structured sol-gel
layer comprises a content of SiO2 of 10 to 70% by weight.

6. The composite according to claim 1, wherein the structured sol-gel
layer has an inorganic degree of cross-linking of higher than 70%.

7. The composite according to claim 1, wherein the structured sol-gel
layer comprises a content of beta-OH of 0.01 to 100/mm.

8. The composite according to claim 1, wherein the least one polysiloxane
has a degree of substitution of 0.5 to 1.5.

9. The composite according to claim 1, wherein the least one polysiloxane
is a polyester-modified polysiloxane.

10. A method for the production of a composite, comprising the steps of:
coating a substrate with a coating composition to obtain a primary
sol-gel layer on the substrate; incorporating a structure into the
primary sol-gel layer; and curing the primary sol-gel layer.

11. The method according to claim 10, wherein the coating composition
comprises at least one alkoxysilane and at least one polysiloxane.

12. The method according to claim 11, wherein the at least one
polysiloxane has a mean molecular weight of at least 1,500 and at most
300,000 g/mol.

13. The method according to claim 10, wherein the step of curing the
primary sol-gel layer comprises curing to a modulus of elasticity of 200
to 10,000 N/mm.sup.2.

14. The method according to claim 10, wherein the step of incorporating a
structure into the primary sol-gel layer comprises stamping the structure
to a structure depth of 2 μm to 200 μm.

15. The method according to claim 10, wherein the primary sol-gel layer
comprises a content of SiO2 of 10 to 70% by weight.

16. The method according to claim 10, wherein the primary sol-gel layer
has an inorganic degree of cross-linking of higher than 70%.

17. The method according to claim 10, wherein the primary sol-gel layer
comprises a content of beta-OH of 0.01 to 100/mm.

18. The method according to claim 10, wherein the least one polysiloxane
has a degree of substitution of 0.5 to 1.5.

19. The method according to claim 10, wherein the least one polysiloxane
is a polyester-modified polysiloxane.

[0003] This invention relates to a composite with a substrate and a
sol-gel layer applied to said substrate as well as a method for the
production of the composite.

[0004] 2. Description of Related Art

[0005] In prior art a lot of methods for providing substrates with
coatings are known, in particular for incorporating structures to
functionalize the substrates. Inter alia, the method of hot stamping is
known in which a stamp die is brought into contact with a substrate
surface at temperatures which are higher than the softening point of the
substrate. In the case of a glass substrate, normally these temperatures
are higher than 500° C. This method has the disadvantage that the
wear of the forming tool results in high cost. Furthermore, only special
substrates having a special melting and solidifying behavior can be used.
In addition, the size of the structurable area as well as the plurality
of the structures are strongly limited.

[0006] Another approach is to provide the substrate with a polymer layer
to be structured. Then, the polymer layer may, for example, be structured
by means of a stamp die. A substantial disadvantage of such polymer
layers is their insufficient thermal stability due to the high portion of
organic components. Often, such layers are stable only up to about 100
degrees Celsius (° C.).

[0007] Further, there is the method of sol-gel nano-imprint, wherein a
stamp die is pressed into a sol-gel layer and subsequently thermal
cross-linking is conducted. This method can hardly be used with rigid
substrates in large areas. These processes are based on the thixotropic
stamping method. In this case a thixotropic lacquer is structured, and
the form thus obtained is conserved due to the thixotropic properties of
the lacquer. Normally, the fixing action is conducted without contact
with a stamp die in a thermal manner or via UV light. The high
thixotropic properties of the lacquer are achieved by the addition of
respective additives which normally affect the transmittance or the
mechanical resistance as well as the pot life of the lacquer.

[0008] The stamping of solvent containing thin layer lacquers is also
known. In this case, due to the high content of the solvent in the sol
most often only layer thicknesses of up to 5 micrometers (μm) can be
produced in an industrially realizable production step, due to the
sub-optimal network forming and tension crack forming properties in the
production of structured thick layers. Also, the produced thick layers
are only stable at temperatures of up to about 200° C.
respectively show cracks starting with a layer thickness of 5 μm at
higher applied load temperatures.

[0009] Thus, there is a need for providing composites comprising
structurable layers on a substrate which do not show cracks even in the
case of higher layer thicknesses. These composites should be producible
via an economic process and should have excellent temperature stability.
In addition, they should be transparent so that they are suitable for
optical applications.

SUMMARY OF THE INVENTION

[0010] The present invention solves the problems of prior art.

[0011] The composites according to the present invention can be produced
by the method described below. Here, a substrate is provided with a
coating composition to obtain a sol-gel layer.

DETAILED DESCRIPTION

[0012] The composite comprises a substrate which carries a sol-gel layer
on at least one of its surfaces. This sol-gel layer is temperature-stable
and structured. When the method steps described herein are conducted and
when the composition of the coating composition is fulfilled, then a
composite having the desired properties will be obtained. In this case,
the sol-gel layer has a thickness of preferably at least 5 μm, more
preferably at least 10 μm which is higher with respect to
corresponding thicknesses in prior art. This becomes possible by the fact
that the sol-gel layer has a modulus of elasticity of 200 to 10,000
Newtons per millimeter (N/mm2), preferably of 500 to 10,000
N/mm2, due to its composition and also due to the production method
used. This property results in the advantage that the sol-gel layer do
not show cracks even in the case of high applied temperature load.

[0013] The modulus of elasticity is achieved by a high degree of
substitution of the inorganic network in the sol-gel layer. Preferably,
for achieving this property temperature-stable siliconorganic compounds
are used. Thus, a layer is produced, the shrinkage of which is very low
in case of thermal load, whereby accordingly no shrinkage tensions are
caused. Furthermore, a particular flexibility of the layer network is
achieved and layer tension may relax.

[0014] In addition, the sol-gel layer preferably contains at least one
polysiloxane. The polysiloxane supports the adjustment of the required
elasticity. The portion of polysiloxane in the sol-gel layer should
preferably be at least 10% by weight and at most 80% by weight, based on
the sol-gel layer, further preferably at least 35% by weight and at most
65% by weight. According to the present invention, polysiloxanes comprise
siloxane units having the following general formula (I):

RnSiO.sub.(4-n)/2 (n=0, 1, 2, 3) (I)

[0015] Thus, siloxane units may be mono-, di-, tri- and tetrafunctional.
In symbol notation this may be described by the characters M (mono), D
(di), T (tri) and Q (quatro): [M]=R3SiO1/2,
[D]=R2SiO2/2, [T]=RSiO3/2 and [Q]=SiO4/2. The
respective units are called M, D, T and Q units, respectively. Thus, a
network constituted of Q units corresponds to the constitution of quartz
glass.

[0016] A differentiation into the following groups is possible: linear
polysiloxanes having the structure [MDnM] respectively
R3SiO[R2SiO]nSiR3 (e.g. poly(dimethylsiloxane)).
Branched polysiloxanes having trifunctional or tetrafunctional siloxane
units as branching elements. Structure [MnDmTn]. In this
case, the branching site(s) is/are located in a chain or a ring. Cyclic
polysiloxanes have ringlike form consisting of difunctional siloxane
units. Structure [Dn].

[0017] Here, the silicon atoms in the polysiloxane polymer may carry
different substituents which are independently selected from each other.
In this case, preferably the groups R are selected independently from
each other from the group consisting of methyl, ethyl, propyl, butyl,
pentyl, hexyl, phenyl and/or epoxy, vinyl, allyl as well as fluorinated
alkyl; wherein methyl- and/or phenyl-substituted polysiloxanes are
particularly preferable. In one polymer there may also be present
different ones of the before-mentioned groups R. When these polysiloxanes
are selected, then the elasticity of the sol-gel layer is further
improved and thus a more resistant layer will be obtained. In particular,
methyl- and/or phenyl-substituted organo-polysiloxanes provide a sol-gel
layer with good heat resistance. Basically, there is one relationship:
the higher the number of phenyl groups in the polysiloxane, the better
the temperature resistance of the sol-gel layer.

[0018] In a particular embodiment according to the present invention the
polysiloxanes are characterized by a high portion of T units of
preferably >80%, particularly preferably >90%. Here, the numerical
portion of the T units of all siloxane units in the polysiloxane molecule
is meant. In a further embodiment according to the present invention the
used polysiloxane is characterized by a portion of D units of about 5 to
40%. With the portion of the T and D units of the polysiloxane, inter
alia, the E modulus according to the present invention of the layers may
be adjusted. A higher portion of T units increases and a higher portion
of D units decreases the E modulus.

[0019] In particular, according to the present invention also oligo, poly
and/or polyhedral silsesquisiloxanes may be used as polysiloxanes.

[0020] Suitable polysiloxanes are described for example in U.S. Pat. No.
3,585,065; 4,107,148; 3,170,890 and 4,879,344. With this reference, the
content of these publications is incorporated into this specification.

[0022] Respective polyester-modified polysiloxanes are sold for example by
Evonik Industries under the trade names Silikoftal HTT, Silikoftal HTL,
Silikoftal HTL-2, Silikoftal HTL-3 and Silikoftal HTS. Thus,
polysiloxanes are meant which have a polyester portion preferably being
covalently bonded to the polysiloxane.

[0023] In this case, the content of polyester in the polyester-modified
polysiloxanes may be 5 to 80% by weight, particularly preferably 20 to
70% by weight, particularly preferably 30 to 50% by weight, based on the
solid content of the polysiloxane. With the polyester content of the
polysiloxane also the E modulus of the polysiloxane-modified sol-gel
layer may be adjusted. Preferably, in this case the portion of polyester
of the polyester-modified polysiloxane consists of reaction products of
epsilon-caprolactone, phthalic acid, trimethylolpropane, ethylene glycol,
diethylene glycol, propylene glycol, glycerin, bisphenol A,
pentaerythritol, trimethylolethane, trimethylolpropane glucose,
1,4-cyclohexanedimethanol, polyvinyl alcohol and/or neopentyl glycol.

[0024] In a preferable embodiment the mean molecular mass (number average)
of the portion of polyester of the polyester-modified polysiloxane is
between 1,000 and 50,000 g/mol, preferably between 1,500 and 30,000
g/mol, particularly preferably between 2,000 and 25,000 g/mol.

[0025] Furthermore, the layer shrinkage and thus the tendency to the
formation of cracks of the structured layers can considerably be
minimized by the use of polyester-modified polysiloxanes.

[0026] In a particular weatherproof embodiment according to the present
invention, in the polyester-modified polysiloxane also linear
dicarboxylic acids, such as for example adipic acid, are contained. With
the addition of these linear carboxylic acids also the E modulus of the
layer may be adjusted. Preferably, the linear dicarboxylic acids are
covalently bonded in the polyester; then they are a structure element of
the polymer.

[0027] Also the incorporation of the polyester-modified polysiloxanes into
the sol-gel network is conducted under heat by reaction with the alkoxy
and/or hydroxyl groups of the polysiloxane network and/or polyester
network. Here, during the reaction water or alcohol is eliminated and a
covalent linkage of Si--O--Si and/or Si--O--C is formed.

[0028] In a particular embodiment according to the present invention the
incorporation of the polysiloxanes into the sol-gel network is achieved
via hydrogen bonds.

[0029] To guarantee the required temperature stability, typically the
polysiloxane should have a degree of substitution of between 0.5 to 1.5,
preferably 1.0 to 1.5. The degree of substitution means the mean number
of alkyl and aryl substituents R according to formula (I) per silicon
atom in the polysiloxane. Preferably, polysiloxanes are used which have a
tendency to self-condensation at high use temperatures. For that a high
hydroxyl functionality and/or functionalization with alcoholate groups is
necessary which according to the present invention is 1 to 7.5% by weight
hydroxyl and/or alcoholate groups, preferably 2 to 5% by weight, based on
the polysiloxane. Furthermore, the high portion of hydroxyl and/or
alcoholate group functionalities is necessary for a covalent bonding of
the polysiloxane precursor via Si--O--Si linkages into the
hybrid-polymeric sol-gel network.

[0030] For the adjustment of the optical layer properties according to the
present invention it is important that the selected polysiloxane (resin
or in solution) is compatible with the hybrid-polymeric sol-gel
component. This preferably means that the polysiloxane is reactively
incorporated into the sol-gel network via a condensation reaction.

[0031] In this case it is important that the polysiloxane is homogenously
incorporated into the layer network and thus for example no phase
separation and thus defects in the layers such as hazing, scattering,
refractive index variations or layer inhomogeneities are caused. The
present inventors have found that for this purpose in particular a
special kind of polysiloxanes is suitable. In this case, the content of
hydroxyl groups and the content of alcoholate groups in the siloxanes,
the degree of cross-linking, the mean molecular mass, the content of
SiO2, the content of further organic additives, such as for example
polyester, and the ratio of phenyl to methyl groups have to be
considered.

[0032] In addition, the pot life and/or the screen printing ability and/or
the residence time of the sol-gel precursor on the screen are affected by
the selection of the polysiloxane. For that the content of the alcoholate
groups, the content of the silanol groups, the portion of fluorine and/or
epoxide groups of the used polysiloxane are important.

[0033] Further, the stampability of the sol-gel precursor and the achieved
layer thickness are affected by the selection of the polysiloxane. Here
in particular the portion of T and D units in the polysiloxane, the
portion of polyester, the portion of fluorine and the portion of epoxide
groups of the used polysiloxane are important.

[0034] For an optimum adjustment of the properties according to the
present invention polysiloxanes should be used the viscosity of which is
in the range of between 0.1 and 10 Pas, preferably between 2 and 5 Pas,
at 150° C.

[0035] The preferable polysiloxanes have a content of hydroxyl and/or a
content of alcoholate groups of 1.0 to 7.5% by weight, preferably 2 to 6%
by weight, based on the weight of the polysiloxane.

[0036] Preferably, the ratio of phenyl to methyl in the used polysiloxane
should be 1.0/1 to 2.7/1, more preferably 1.0/1 to 1.3/1 and most
preferably 1.1/1 to 1.2/1.

[0037] Preferably, a mixture of polysiloxanes and/or
polysilsesquisiloxanes is used. Particularly preferably, a mixture of
polyester-modified polysiloxanes and/or phenyl/methyl-substituted
polysiloxanes and fluorinated and/or epoxide-functionalized polysiloxanes
is used. In this case, the portion of the fluorinated and/or
epoxide-functionalized polysiloxanes in the total mass of polysiloxanes
is preferably <5% by weight, particularly preferably <2% by weight.
The portion of polyester-modified siloxanes in the total mass of
polysiloxanes is preferably higher than 50% by weight, particularly
preferably higher than 80% by weight.

[0038] Preferably, the glass transition temperature of the polysiloxane
should be higher than 40° C., preferably even higher than
45° C. To minimize the shrinkage of the first layer during the
production, a polysiloxane should be used which contains 0.2% by weight
or less of organic solvents, preferably even 0.1% by weight or less of
organic solvents.

[0039] Preferably, here a polysiloxane resin is used. In addition, this
resin is characterized in a particular embodiment by a content of
SiO2 of 50% by weight to 65% by weight, preferably 50% by weight to
55% by weight, determined after thermal load at 700° C. In a
special embodiment according to the present invention the content of
SiO2 of the polysiloxane may also be 75% by weight to 85% by weight.
In this case, the content of SiO2 is determined by the pyrolyse loss
after a thermal treatment at 1,000° C. for 1 h. For example, this
determination may also be conducted by the method of thermography which
is known by a person skilled in the art. A suitable method may for
example be found in H. Geβwein, "Entwicklung hochfester Net shape
Oxidkeramiken im System Al2O3--SiO2--ZrO2",
Forschungszentrum Karlsruhe, Wissenschaftliche Berichte, FZKA7186, 2005.

[0040] In a particular embodiment the preferable mean molecular mass of
the used polysiloxane and/or polysilsesquisiloxane is between 1,500 and
300,000 g/mol, preferably between 2,000 and 5,000 g/mol and/or between
200,000 and 300,000 g/mol and/or of 1,500 to 2,500 g/mol. In other words,
also mixtures of different polysiloxanes having different molecular
weights may be added. If nothing else is indicated herein, the mean
molecular mass is supposed to be the number average Mn.

[0041] The composite may be produced by a method which comprises the
following steps: coating a substrate with a coating composition so that
at least on one surface of the substrate a primary layer is obtained, and
curing the layer to obtain a sol-gel layer.

[0042] During the curing of the layer the sol-gel conversion takes places
during which the coating composition (the sol) is converted into the gel.
Subsequently, optional further curing steps may follow which are
described below.

[0043] The advantage of this method with respect to prior art methods
inter alia is that with the described method a method is available which
allows a great freedom of design. It facilitates the provision of layers
also on locally limited areas, finely structured or as a complete area on
a rigid material, such as glass or glass ceramic. And this method can be
conducted with reproducible results and allows the production of
identical articles with respective structured layers.

[0044] Before curing the sol-gel layer on the substrate thus produced is
provided with a structure. This is preferably conducted with the help of
a stamp die which is described below.

[0045] In a preferable embodiment of the method according to the present
invention this method further comprises the step of: coating the sol-gel
layer with a functional layer.

[0046] The functional layer may provide the sol-gel layer with further
properties in the sense of a surface functionalization. This may for
example be achieved by coating with a hydrophobic coating solution. So
the effect is achieved that the surface thus coated is provided with
improved dirt-repellent properties. It is also possible to coat the
sol-gel layer with a metal layer or a lacquer layer.

[0047] As described above, the sol-gel layer is modified by the
incorporation of a structure. Preferably, with this method structures
with optical functions are incorporated, such as diffractive or
refractive structures.

[0048] The sol-gel layer in the composite may be structured such that a
depth of the structure of higher than 5 μm, preferably higher than 20
μm and particularly preferably up to 200 μm, further preferably 10
μm to 50 μm is achieved.

[0049] An embodiment of the sol-gel layer according to the present
invention preferably withstands temperature loads of at least 170°
C., in particular 220° C. and preferably even 250° C. at
least for 10 minutes. The sol-gel layer has a high layer thickness to
facilitate the depths of the structures. It is surprising that with the
material according to the present invention and the method according to
the present invention such high layer thicknesses which are free of
cracks and temperature-stable can be produced. Primarily, this is
achieved by the composition of the sol-gel layer which in turn can be
achieved by the use of a suitable coating composition and strict
adherence of the method according to the present invention.

[0050] The composite according to the present invention does not only have
high temperature stability, but does not discolor also under the exposure
of temperatures of for example 250° C., but retains its optical
properties. In an embodiment according to the present invention this
feature can be explained, inter alia, by the use of a polyester-modified
polysiloxane.

[0051] Furthermore, the composite is particularly weather and UV resistant
due to its hybrid-polymeric composition and the siloxane modification.

[0052] With the structuring of the surface and the variation of the
composition of the sol-gel layer can be achieved that the layer is
provided with dirt-repellent properties.

[0053] The sol-gel layers are designed such that they have high
adhesiveness to the substrate. Thus, an adhesive is not required and
according to the present invention preferably no further layer, in
particular no adhesive layer, is present between the substrate and the
sol-gel layer.

[0054] Due to the composition of the sol-gel layer this layer is a dense
layer which is nearly free from pores. Nearly free from pores means that
the layer has a porosity of lower than 10% by volume, preferably lower
than 5% by volume, particularly preferably lower than 2% by volume.

[0055] The method according to the present invention has the advantage
that it needs only very small amounts of organic solvents which has
positive effects with respect to environmental compatibility and safety
at work. Furthermore, with the coating composition of the sol described
below it is guaranteed that sufficient process stability due to the
optimization of the pot life of the sol is achieved.

[0056] When the method according to the present invention is used, then a
structure reproducibility of higher than 80%, preferably higher than 90%
with respect to the master piece which is described below can be
achieved.

[0057] The reason for the excellent properties of the sol-gel layer is
that it comprises a hybrid-polymeric sol-gel material preferably modified
with a polysiloxane. Thus, the particular properties with respect to the
modulus of elasticity, but also the surface energy, the mechanical and
chemical resistance and the possible transparency are achieved.
Furthermore, this method may be used in industry so that the composites
can be produced in a cost-effective manner.

[0058] The sol-gel layer can be applied in large areas very easily--as can
be seen from the method described below. Preferably, even the whole
surface of the substrate is provided with the sol-gel layer. Here, the
size of the area to be coated is preferably at least 0.1 m2, further
preferably at least 0.25 m2. Preferably, the sol-gel layer is
provided with a structure on the whole surface thereof which preferably
has been incorporated according to the method described below. In
preferable embodiments the structured area has a size of at least 0.1
m2, further preferably at least 0.25m2.

[0059] Preferably, the substrates are rigid substrates. Rigid substrates
are substrates which often consist of brittle breaking materials such as
for example polymers, glass, ceramic or glass ceramic. Generally, rigid
substrates are glasses, ceramics and glass ceramics having thicknesses of
the substrate of preferably 0.3 to 100 mm, further preferably 10 to 50
mm. These may for example be iron containing or iron reduced soda-lime
glasses, corrosion resistant glasses, such as borosilicate glass,
aluminosilicate glass or alkali reduced glasses, optical glasses having
specially adjusted optical dispersion properties, such as for example
being sold by Schott AG or Corning, or transparent or volume-colored
glass ceramics. In this case, rigid substrates may be chemically or
thermally tempered.

[0060] In a particular embodiment the substrate may be a tube or an
already curved substrate having a radius of curvature of 0.05 to 1,000 m,
preferably 1 to 50 m.

[0061] The refractive structures which are preferably present in the
sol-gel layer have preferably a depth of the structure of higher than 5
μm. When diffractive structures are incorporated, preferably they have
a depth of the structure of higher than 0.2 μm. Preferably, the
sol-gel layers have refractive and diffractive structures.

[0062] When structures with a decorative function are incorporated into
the sol-gel layer, then they have a stochastic roughness with a depth of
the structure of 200 nm to 100 μm. When a brush-finished surface is
produced, then the stamping has a depth of the structure of smaller than
5,000 nm, preferably smaller than 3,000 nm, particularly preferably
smaller than 1,500 nm.

[0063] "Depth of the structure" means the mean depth of the structure
stamped into the layer. Preferably, the sol-gel layer has a macroscopic
lateral structure which can be applied by means of screen printing,
tampon printing, inkjet printing or offset printing in a cost-effective
manner. Here a lateral structure means that the lacquer has been applied
only locally onto the substrate and that this lacquer has been structured
later by the stamping method. Thus, due to the coating method the
substrate surface is not completely coated and thus also not completely
structured. In this case, the lateral resolution of the structure is
>10 μm, particularly preferably >20 μm, especially
particularly preferably >100 μm due to the resolution of the
coating method used. The lateral resolution of the screening method which
typically can be achieved is >20 μm.

[0064] The sol-gel layer according to the present invention is designed
such that it can be prepared in one single coating step, preferably by
means of screen printing. In preferable embodiments the layer is stamped,
thus has a stamping.

[0065] For the incorporation of structures preferably at first a master
piece is prepared, as is described below.

[0066] When the sol-gel layer should be structured by a stamping step,
then a stamp die is necessary. The production of the stamp die requires
according to the present invention the use of a so-called master piece.
The master piece is an article which carries the structure to be realized
later in the sol-gel layer. Thus, the master piece is the basis for the
form of the structure of the sol-gel layer. Thus it is guaranteed that
also in the case when a stamp die has become worn-out in the course of
time an identical stamp die can again be produced starting from the
master piece. Therefore, it preferably consists of a durable material,
such as for example of metal.

[0067] In an alternative way, of course also a stamp die may simply be
prepared by directly incorporating the structure of the sol-gel layer to
be realized in negative form into a green stamp die body. In this way, in
a simple manner a model can be formed which preferably has been cleaned
before.

[0068] Preferably, the master piece should be cleaned before use so that
it is free of dust and fluff. For the production of the stamp die,
preferably then the master piece is brought into contact with the polymer
mass, so that the structure of the master piece is transferred to the
polymer mass. In preferable embodiments the polymer mass is cast onto the
clean master piece. Preferably, the polymer mass is a silicone molding
material. After the transfer of the master structure to the polymer mass,
preferably the mass is hardened. The hardening is conducted by the use of
methods which are known by a person skilled in the art, preferably
however by the use of heat.

[0069] Sometimes, complex structures may include bubbles between the
polymer mass and the master piece. Preferably, they are removed by the
use of low pressure. The stamp die thus obtained is removed from the
model and normally can be used immediately. After a step of stamping
these stamp dies can be cleaned by means of normal cleaning solutions, in
particular with ethanol or isopropanol, and used again.

[0070] In a step of coating the substrate a coating composition is applied
which forms the primary layer. The coating composition is a sol, thus
preferably a colloid dispersion. After sol-gel conversion the coating
composition may form a solid layer on the substrate. The step of coating
the substrate can be realized in a continuous and cost-effective
precipitation method which thus is suitable for production. This can be
realized with a method in which the primary layer of the coating
composition, thus the sol-gel layer, is applied on one side of the
surface of the substrate by means of a liquid coating method. The
possible liquid coating methods are known by a person skilled in the art.

[0071] In a preferable embodiment the coating composition is designed such
that it can be applied by means of screen printing. So a partial
application of the primary layer is facilitated. This results in a
significant advantage: by the fact that areas which should not be
provided with the sol-gel layer can be maintained and free areas which
are often required for display uses, touch uses or bonded joints do not
contain a structured layer, in these areas no time-consuming control of
layer unevenness, inhomogeneities and impurities is necessary.

[0072] As the coating method one-sided screen printing, tampon printing,
dip coating, roll coating, flow coating, coating with a doctor knife,
spraying or other normal liquid coating technologies may be used. The
substrates may be coated one-sided, two-sided or multiple-sided. Screen
printing is particularly preferable because therewith an already
laterally structured primary layer can be applied.

[0073] The coating composition optionally comprises particles, wherein
preferably the particles are nanoparticles. The particles may be of
amorphous, hybrid or crystalline kind. According to the present invention
also mixtures of different kinds of particles may be used. With the
material composition of the particles, inter alia, an adjustment of the
refractive index of the structured layer with respect to the substrate
and/or the functional layer may be realized. In preferable embodiments
the particles are selected such that the structured layer itself is
functionalized so that preferably no separate functional layer is
necessary any longer. So for example it is possible to incorporate
conductive particles to prevent electrostatic charge. In a further
embodiment in the structured layer hydrophobic particles are contained.
In a further embodiment the structured layer is photocatalytically active
and/or the refractive index of the layer is adjusted in a targeted manner
due to the addition of titanium oxide (TiO2). Particularly
preferable are silicon dioxide (SiO2) particles, because with their
use a shrinkage of the structure of only 0 to 25%, based on the depth of
the structure of the master piece, can be achieved. Of course, in
preferable embodiments the particles which can be added to the coating
composition are contained in the sol-gel layer of the composite.

[0074] Preferably, the particles have an irregular form and/or the form of
a fiber. Preferably, the particles have diameters of 5 to 15 nm and
preferably lengths of 5 to 150 nm. In an alternative, also particles
having different sizes of 5 to 125 nm can be used. The particles may also
have the form of spheres. Unless indicated otherwise, in this
specification the information given with respect to the size of particles
means the diameter according to Ferret, determined according to the
method of dynamic light scattering.

[0075] The coating composition comprises sol-gel precursors. Preferably,
alkoxysilanes are used as sol-gel precursors. Preferable are
alkoxysilanes which are functionalized with organically cross-linkable
groups. Particularly preferably these are epoxy-functionalized and
methacrylate-functionalized alkoxysilanes. For a special embodiment
according to the present invention, particularly preferable UV excitable
radically polymerizable hybrid-polymers are used.

[0077] In a particular embodiment inorganic SiO2 nanoparticles are
added to the coating composition. Preferably, the portion by volume of
the nanoparticles of the coating composition is higher than 10%, further
preferably higher than 20%. Preferably, the nanoparticles are added as an
alcoholic dispersion.

[0079] In an embodiment the particle size of the sol-gel precursor is in a
range of 0.05 to 200 nanometers (nm), particularly preferably of 1 to 100
nm. Here in particular the form of the particles may be spherical and/or
also irregular.

[0080] In a particular embodiment according to the present invention
nanoparticles having a high refractive index of higher than 2.1,
particularly preferable of higher than 2.3 are added to the
polysiloxane-modified sol-gel precursor. For example, anatase has a
refractive index of higher than 2.5 and rutile has a refractive index of
higher than 2.7. In this case the portion by mass of amorphous and/or
crystalline particles, based on the total content of solids in the layer,
is preferably higher than 5% by weight, particularly preferably higher
than 10% by weight.

[0081] In a particularly preferable embodiment as a sol-gel precursor the
coating composition comprises a UV curable hybrid-polymeric, hydrolyzed
and condensed alkoxysilane precursor, in particular
glycidylpropyltriethoxysilane and/or glycidylpropyltrimethoxysilane
and/or methacryloxypropyltriethoxysilane and/or
methacryloxypropyltrimethoxysilane and/or
methacryloxypropylmethyldiethoxysilane and/or
methacryloxypropylmethyldimethoxysilane which are functionalized with
polysiloxanes. Preferably, methyl- and/or phenyl-functionalized
polysiloxanes are used. Thus preferably, the sol-gel layer on the
substrate comprises the reaction products of sol-gel precursors which are
described herein, in particular alkoxysilanes, with polysiloxanes which
are described herein.

[0082] Here, preferably as the sol-gel precursor a hybrid-polymer which is
derived from a sol-gel is used which has been obtained from a reaction of
a silane having the general formula R1Si(OR)3 and optionally
R2Si(OR)3 or R1R2Si(OR)2 with a
tetraalkoxysilane having the general formula Si(OR)4 in the context
of an acidic hydrolysis and condensation reaction. Preferably, R1 is
a UV curable organic function, preferably a radically polymerizable
function, especially preferably a methacrylate-based function. OR is an
alcoholate group, preferably ethylate. R2 is an aromatic or
aliphatic organic group, preferably methyl and/or phenyl. Preferably, the
sol-gel precursor is characterized in that the ratio of T to Q units is
3:1 to 5:1, preferably 3.5:1 to 4.5:1. In the preferable embodiment the
sol-gel precursor is characterized in that it does not contain M and/or D
units.

[0083] The use of polysiloxanes in the coating composition results in a
more elastic sol-gel layer. The reason for that may be that the degree of
cross-linking of the sol-gel layer is lower than in the case of the use
of monomeric precursors without the addition of polysiloxanes. Already
before, the polysiloxanes have been polymerized to large molecules, and
therefore they disturb the otherwise strongly cross-linked structure in
the sol-gel layer. Also, the polysiloxane precursors have a high portion
of T and/or D units. Probably, this is the reason for the elasticity and
temperature resistance according to the present invention of the sol-gel
layers of this invention.

[0085] In preferable embodiments one or more amino-functionalized silanes
are added to the coating composition. Preferable amino-functionalized
silanes are 3-aminopropyltrimethoxysilane,
[3-(methylamino)propyl]trimethoxysilane,
[3-(phenylamino)propyl]trimethoxysilane,
[3-(diethylamino)propyl]trimethoxysilane,
3-[2-(2-aminoethylamino)ethylamino]propyltrimethoxysilane,
N-[3-(trimethoxysilyl)propyl]ethylene diamine,
1-[3-(trimethoxysilyl)propyl]urea,
bis(3-(methylamino)propyl)trimethoxysilane and mixtures of these
components. Amino-functionalized silanes improve the cross-linking of the
layer and the adhesion of the layer at the substrate.

[0086] Furthermore, the coating composition may comprise one or more
mercaptosilanes. Mercaptosilanes improve the adhesion of the layer at the
substrate.

[0087] In a preferable embodiment the coating composition comprises
polyfunctional organic monomers and/or organo-silanes. Preferably, these
monomers have 2 or 3 or 4organically cross-linkable functional groups.
Preferable substances of this group are bismethacrylates, bisepoxides,
bismethacrylate silanes, bisepoxide silanes, bismethacrylate urethane
silanes and mixtures of these substances.

[0089] For example, these may be the reaction products of 1 mol
hexamethylene diisocyanate with 2 mol 2-hydroxyethyl methacrylate, of
1mol (tri(6-isocyanatohexyl)biuret with 3 mol hydroxyethyl methacrylate
or of 1 mol trimethylhexamethylene diisocyanate with 2 mol hydroxyethyl
methacrylate. These compounds are also called urethane dimethacrylates.

[0090] As preferable polysiloxanes branched polysiloxanes are used.
Particularly preferably, trifunctional and/or tetrafunctional
polysiloxanes are used. Also preferable are cyclic polysiloxanes and/or
polysiloxanes having the form of a ring.

[0091] In a particular embodiment, to the coating composition so-called
polysilsesquisiloxane compounds (POSS) may be added as polysiloxane.

[0092] The portion of polysiloxane of the sol-gel layer should preferably
be at least 10% by weight and at most 80% by weight, based on the sol-gel
layer, further preferably at least 35% by weight and at most 65% by
weight.

[0093] So that the coating compositions are environmentally friendly, safe
and capable of being applied by screen printing, preferably they have a
content of solvent of not higher than 20% by weight, further preferably
lower than 10% by weight. Preferably, here solvents having a low vapor
pressure of (at room temperature) lower than 2 bar and/or a boiling point
of higher than 120° C. are used. A preferable solvent is
diethylene glycol monoethylether. For that for example in the production
of the coating compositions an exchange of the solvent from volatile
alcohols to diethylene glycol monoethylether is conducted. So it is
achieved that in the screen printing method during the continuous
application of the coating composition the screen will not be clogged.
However in preferable embodiments the coating composition is free of
solvent.

[0094] Preferable, additives are added to the coating solution for
preventing defects, layer unevenness, phase separation effects, bubbles
and/or foaming. These additives may sum up to 5% by weight, preferably up
to 2% by weight of the coating solution. Preferable additives are
deaerators, antifoaming agents, leveling agents and dispersing agents.
They can commercially be sold, for example, from the company TEGO
(EVONIK) and they are known as typical lacquer additives by a person
skilled in the art. Specifically, they are pure and/or organically
modified (with low molecular weight) polysiloxanes, organic polymers,
fluorine-functionalized polymers, polyether-modified polysiloxanes,
polyacrylates and/or basic or acidic fatty acid derivatives.

[0095] In a particular embodiment the coating composition may also contain
UV or thermally cross-linking organic or hybrid-polymeric components. To
initiate the radiation-based polymerization, most often a UV initiator is
added to the coating composition. These photoinitiators which are known
by a person skilled in the art are, for example, prepared under the trade
name Irgacure by the company BASF. In a preferable embodiment according
to the present invention radical photoinitiators are used which can be
excited by wavelengths of higher than 300 nm by means of UV radiation.

[0096] When the coating composition described herein is used, then thick
films can be applied onto the substrate which nearly do not show any
shrinkage with respect to the applied wet film thickness, since they only
contain low amounts of solvents or no solvent at all.

[0097] With some coating compositions it is advisable to pre-cure the
primary layer briefly, wherein preferably the pre-curing treatment takes
place by photochemical processes. This is in particular an advantage,
when subsequently a curing treatment via UV light is envisaged. But this
pre-curing treatment may also be realized by thermal treatment, in
particular by means of an IR radiating facility.

[0098] When the first layer should be structured, then onto the primary
layer a stamp die is applied. This may be conducted in a continuous or
static manner. In one embodiment the stamp die may be provided with a
sol-gel layer. The stamp die will press the desired structure into the
primary layer.

[0099] Preferably, in this step the stamp die is pressed onto the primary
layer with a contact pressure of 0.01 to 5 bar. In a particular
embodiment this step is conducted under vacuum.

[0100] Now, during the optional structuring, a composite comprising at
least the components substrate, primary layer and stamp die is present.
Here, preferably a pressure is applied onto the composite so that the
components are pressed onto each other. Then the primary layer is cured.

[0101] Preferably, the curing treatment is conducted in a thermal and/or
photochemical manner. The photochemical curing treatment is particularly
preferable. In another embodiment no pressure is applied onto the
composite, since the coating composition of the layer to be structured
which is still liquid before the curing treatment is drawn into the
structure of the stamp die by itself.

[0102] In an optional method step bubbles are removed by hand, with a roll
or by means of low pressure, wherein in this case the low pressure is
lower than 900 mbar. By this curing step the structured layer becomes
solid so that the stamp die can be removed.

[0103] As explained above, the structuring step using the stamp die is an
optional step. It is conducted only, when the sol-gel layer should carry
a structure. When no structure is desired, of course the primary layer
may be dried without a stamp die to obtain a sol-gel layer without
structure.

[0104] When the curing of the first layer is conducted in a thermal
manner, then the temperature is in a range of 50 to 150° C. The
photochemical curing is conducted by means of a UV light source having a
maximum emission at a wavelength of 200 to 400 nm.

[0105] In particular embodiments already during this step the hardening
treatment may be conducted. This means that no further step of hardening
is necessary. This curing may be conducted by UV light.

[0106] After curing or optionally hardening the stamp die, if used, will
be removed again. After the removal of the stamp die the sol-gel layer is
present in the form of a structured thick layer. Preferably, the layer
thickness of the sol-gel layer is about up to 200 μm. The structures
which are obtained in the structured layer are defined by the structure
of the stamp die.

[0107] Preferably, the layer thickness of the sol-gel layer is at least 5
μm, preferably at least 10 μm and more preferably at least 20
μm.

[0108] Optionally, the sol-gel layer is hardened after the removal of the
stamp die. In particular, it is thermally hardened, when the first curing
step has been conducted with UV light. Here, besides a further
advantageous cross-linking of the organic monomers primarily also a
further cross-linking (condensation) of the hydroxyl groups (inter alia
with the elimination of the alkoxide groups) of the Si--O network takes
place. So, primarily an advantageous covalent linkage of the polysiloxane
network with the sol-gel network is achieved. Preferably, this
cross-linking reaction is conducted at temperatures of between 150 and
300° C., particularly preferably at temperatures of between 220
and 270° C.

[0109] In alternative embodiments the temperature at which the hardening
is conducted is preferably in a range of 50 to 1,000° C., further
preferably at 100 to 500° C. When organic components of the
sol-gel layer should be burned out, then the temperature is adjusted to
at least 250° C., preferably >300° C., particularly
preferably >500° C. It has been shown that the structure will
be maintained, also in the case that the organic components are
completely burned out. The shrinkage of the structure relative to the
structure of the master piece decreases with decreasing reprocessing
temperature and increasing particle content of the coating composition in
an amount of between 0 and 60%. However, the shrinkage of the structure
can be compensated with a structure of the master piece the depth of
which is somewhat higher than the final desired structure in the sol-gel
layer.

[0110] In a particular embodiment the method is characterized in that the
hardening of the sol-gel layer is conducted in a thermal manner in a
temperature range of 100 to 1,000° C., particularly preferably in
a temperature range of between 450 and 740° C.

[0111] The composition of the sol-gel layer is characterized in that is
contains at least 25 to 100% by weight, particularly preferably 40 to 80%
by weight, especially preferably 45 to 65% by weight of SiO2. In a
special embodiment according to the present invention the content of
SiO2 is 50 to 58% by weight. In this case, the content of SiO2
means the residual solid content of SiO2 after a thermal treatment
of the structured layer material at 700° C. for 1 hour.

[0112] The preferable depth of the structures in the structured sol-gel
layer varies in a range of 1 μm to 100 μm, preferably of 4 μm to
40 μm, particularly preferably of 10 to 30 μm. Periodic or
statistic structures may be used as structures, wherein preferable
structures are lens structures, sinusoidal structures, refractive line
grids, refractive cross grids, diffractive line grids, diffractive cross
grids, diffractive moth eye structures, diffractive optical elements,
numbers, codes, in particular barcodes and/or product codes, pyramidal
structures, inverted pyramidal structures, safety features, holographic
structures, uncoupling structures for OLEDs or for LEDs, scattering
structures for light elements and/or light guide structures for day light
for storefronts or ceiling elements. But there can also be reproduced
lines of a brush-finished surface, scattering layers of different kinds
and etched surfaces as well as haptic structures.

[0113] The sol-gel layer is responsible for the structure of the
subsequent layers. This means that a functional layer which is
subsequently applied such as for example a metal layer or a lacquer layer
preferably will adopt the surface structure of the sol-gel layer.

[0114] Preferably, the coating composition contains hydrolyzed and
condensed epoxy- or methacrylate-functionalized alkoxysilanes as sol-gel
precursors. Therefore, the sol-gel layer contains the hybrid-polymers
originated from them. Particularly advantageous is the use of
epoxide-functionalized alkoxysilanes, because with them the shrinkage of
the structure is reduced which allows better structure accurateness.

[0115] When the sol-gel layers are prepared according to this invention,
preferably they have an inorganic degree of cross-linking of higher than
70%, preferably higher than 80%. This results in the advantages according
to the present invention, in particular with respect to the elasticity
and the resistance of the layer. The inorganic degree of cross-linking is
determined with the help of 29Si-NMR.

[0116] So that this can be achieved, preferably the coating composition
should contain methyl-, ethyl- or phenyl-substituted alkoxysilanes during
the production method. Alternatively, also further organically
cross-linking components may be contained.

[0117] Preferably, the sol-gel layer contains a composite material being a
reaction product of a polysiloxane with at least one alkoxysilane. With a
production according to the present invention this composite has a degree
of substitution of 0.5 to 1.5, preferably 0.7 to 1.5 and particularly
preferably 0.8 to 1.3. The degree of substitution is the mean number of
silicon-carbon bonds per silicon atom in the composite. The degree of
substitution may be determined via 29Si-NMR.

[0118] Preferably, the sol-gel layer comprises the hybrid-polymer of
alkoxysilane precursors, wherein as an alkoxysilane precursor in
particular (3-glycidoxypropyl)triethoxysilane and
(3-methacryloxypropyl)trimethoxysilane are preferable. Preferably, the
polysiloxane added is a phenylmethylpolysiloxane.

[0119] The content of hydroxyl groups of this composite material is 1 to
5% by weight, preferably 1 to 4% by weight.

[0120] The silicon-carbon ratio (Si:C ratio) is the ratio of the amounts
of substance of silicon to carbon in the composite material of the
sol-gel layer. Preferably, this ratio is 20:1 to 1:5, in particular 10:1
to 1:2 and particularly preferably 7:1 to 2:1. This ratio may be
determined via an elementary analysis.

[0121] Preferably, the organic degree of cross-linking of the sol-gel
layer is higher than 30%, particularly preferably higher than 50%. This
degree of cross-linking is determined by means of Raman measurement and,
for example, is conducted via a measurement of the intensity of the band
of the epoxy ring at 1269 cm-1. As a comparison the band of the
vibration belonging to CH2 at 1299 cm-1 is used.

[0122] Preferably, due to the preferable production method the sol-gel
layer has a content of beta-OH of 0.01 to 100/mm, preferably 0.05 to
10/mm and in particular 0.1 to 2/mm. The measurement of the content of
beta-OH is conducted according to the method described in WO 2009/998915.
The layer thicknesses of the layers were between 10 and 50 μm.

[0123] The low content of beta-OH is directly connected with a low surface
energy of the sol-gel layer. Therefore, the sol-gel layers according to
the present invention have a low surface energy, about with a polar
portion of preferably lower than 25 mN/m, in particular lower than 15
mN/m and a disperse portion of preferably lower than 40 mN/m, in
particular lower than 35 mN/m. This effect results in a contact angle
with respect to water of preferably higher than 50°, in particular
higher than 75° and preferably higher than 85°, whereby the
sol-gel layer is provided with hydrophobic properties and thus a certain
dirt-repellent effect. Primarily, the reason for this effect is the
sol-gel layer as such and not its optional structure, wherein the high
degree of substitution of the Si--O network and the low porosity
significantly contribute to this effect. By a stamped structure said
effect may be increased in addition. In a particular embodiment a
superhydrophobic and superoleophobic surface can be produced.

[0124] Preferably, the maximum mass loss of the sol-gel layer after a load
of 300° C. for half an hour is 30% by weight, particularly
preferably 15% by weight due to the high degree of substitution of the
network.

[0125] According to the present invention the composites may comprise a
plurality of substrates. With the method according to the present
invention layers may be built on nearly any substrate. Since this
invention allows the adjustment of the refractive index of sol-gel layers
to the refractive index of the substrate by the targeted use of
particles, even transparent composites may be obtained. This may
advantageously be used in the coating according to the present invention
of transparent substrates. Therefore, transparent substrates are
particularly preferable. In one embodiment the substrate is selected from
transparent plastics, such as polycarbonates, polyacrylates, polyolefins
and cycloolefinic copolymers.

[0126] However, particularly preferable are inorganic substrates, since
most often they have a better temperature resistance than organic
substrates. Particularly preferable are soda-lime glasses, in particular
iron-poor soda-lime glasses, borosilicate glasses, aluminosilicate
glasses and glass ceramics, in particular transparent glass ceramics, as
well as laminates of different glasses, glass ceramics and/or ceramics.
The glasses may be chemically and/or thermally tempered and may have the
form of a ring and/or may have a curved form. The glasses may be in the
form of vials, ampoules or syringes.

[0127] Also the use of the described composites in micro-lens systems,
pharmaceutical packages, light guide systems in the field of
architecture, composite materials for illumination technique, uncoupling
layers for OLEDs and uncoupling layers for LEDs, preferably on curved
substrates is according to the present invention.

[0128] The method according to the present invention allows the direct
application of the desired layers with or without surface structure onto
a finished product.

[0129] At the same time, the sol-gel layers according to the present
invention have a function as a barrier, in particular with respect to
diffusion.

[0130] In special embodiments before the coating step a primer is applied
onto the surface of the substrate.

[0131] In preferable embodiments a step of conditioning of the surface of
the substrate is conducted.

[0132] In a further embodiment the sol-gel layer is provided with at least
one functional layer. The functional layer may have an antistatic,
hydrophobic, hydrophilic, oleophobic, photo-catalytic, thermo-catalytic,
reflective, optically active, colored and/or electrically conducting
design.

[0133] In a preferable embodiment the substrate with the sol-gel layer has
a transmittance of >90% and an absorption of <5%, preferably
<2%, particularly preferably <1% in a wavelength range of 300 to
800 nm and a layer thickness of 5 μm, preferably even 10 μm.

[0134] Preferably, the refractive index of a particular embodiment
according to the present invention of the sol-gel layer is between 1.4
and 1.6. Preferably, it is 1.45 to 1.55. In a further embodiment
according to the present invention the refractive index of the
polysiloxane-modified sol-gel layer is between 1.6 and 1.7. Preferably,
it is adjusted to the substrate and the difference to the refractive
index of the substrate used is not higher than 0.05 points.

[0135] The modulus of elasticity of the layers according to the present
invention after UV curing is 200 to 4,000 N/mm2, preferably 300 to
3,000 N/mm2, particularly preferably 500 to 2,000 N/mm2.

[0136] The modulus of elasticity of the layers according to the present
invention after thermal curing at 140 to 300° C. is 500 to 10,000
N/mm2, preferably 750 to 6,000 N/mm2, particularly preferably
1,250 to 5,000 N/mm2.

[0137] In other words, preferably the modulus of elasticity of the sol-gel
layers according to the present invention is 200 to 4,000 N/mm2 or
500 to 10,000 N/mm2. Preferably, in another preferable embodiment
the modulus of elasticity is 500 to 4,000 N/mm2 or >4,000 to
10,000 N/mm2. The mechanical properties, in particular the Young's
modulus of elasticity of the layers according to the present invention
are preferably determined by the use of a nano-indenter respectively are
calculated from the nano-indenter measurement. A person skilled in the
art will know such methods from literature. The methods are in accordance
with the model of Hertz, such as for example described of Q. Liao et al.
in Mech. of Mat. 42 (2010) 1043-1047 or in Thin Solid Films 516 (2008)
1056 to 1062.

[0139] In a preferable embodiment the structured sol-gel layer comprises a
decorative layer for cover plates of glass, such as can be used for
example in the field of household appliances or in the field of
architecture (for indoor and outdoor use) or automotive industry or in
the field of aircraft construction or mechanical engineering (for example
elevators). The decorative layer is stamped into the sol-gel layer. In
this case a cover plate is characterized in that it acts as a kind of
faceplate. In prior art such faceplates are for example made of stainless
steel.

[0140] Thus, according to the present invention the composite may be used
in or as doors of a refrigerator, baking oven panes, steamers, cooking
plates for gas usage, glass cutting boards, linings for TV sets or
electronic devices, exhaust hoods and elevators. In this case structures
can be incorporated into the sol-gel layer imitating the appearance of
brushed metal or the surface of sandblasted and/or etched glass. Then,
the respective structures can simply be used as a master piece to provide
the above-described stamp die.

[0141] Normally, here statistic structures are used which have a depth of
the structure of 40 nm to 10 μm. In the case of brushed stainless
steel structures they are for example structures of brush marks of round
or linear form having a depth of preferably up to 3 μm, particularly
preferably up to a depth of the structure of 2 μm.

[0142] In a particular embodiment one or more layers having metallic
appearance are applied onto the structured layer by a liquid coating
method or a deposition method, such as for example sputtering or CVD, for
achieving the optical appearance of stainless steel. In this case, these
layers having metallic appearance may consist of metal or a semimetal or
an organic and/or an inorganic lacquer. Preferably used are metal layers
having a color point of stainless steel, chromium, aluminium, copper,
platinum or rhodium. Preferably, for the deposition of a layer having
metallic appearance the sputtering method and/or a lustre color and/or a
pigmented sol-gel color and/or a pigmented or colored organic paint are
used.

[0143] In this case the thickness of the layer having metallic appearance
is between 50 and 500 nm, preferably between 60 and 200 nm. Preferably, a
stainless steel target, a Cr target, a Cu target and/or an Al target are
used for the production of the layers having metallic appearance via the
sputtering method. In a particular embodiment the color point of the Cr
layer is adjusted to the color point of stainless steel by suitable
process management.

[0144] In a particular embodiment the layer having metallic appearance may
be provided with several protective layers. Furthermore, in a preferable
embodiment onto the layer having metallic appearance an organic,
polysiloxane-based and/or sol-gel-based sealing layer may be applied.
This e.g. may be an epoxy- and/or polyurethane-based scratch proof
coating (BSH test>1,000 g).

EXAMPLE 1

[0145] During Example 1, 0.06 mol of GPTES
(glycidoxypropyltriethoxysilane) and 0.02 mol of TEOS (tetraethoxysilane)
and 0.02 mol of PTEOS (phenyltriethoxysilane) were added into a vessel
and hydrolyzed with 2.3 g of water in which 0.344 g of PTSH (para-toluene
sulfonic acid) had been solved. After stirring for three hours the
volatile reaction products were removed with a rotary evaporator. In 10 g
of the hydrolyzate such obtained 5 g of a polysiloxane resin having a
ratio of phenyl to methyl of 1.2/1 and a molecular mass of 2,000 to 7,000
and a content of SiO2 of about 52% were solved.

[0146] Subsequently, 1.5 ml of a solution of 20% of the cationic
photoinitiator Irgacure® 250 in 1-methoxy-2-propanol were added to
the coating composition. Subsequently, the volatile components were
removed with a rotary evaporator.

[0147] With the help of doctor knifes using a gap width of 90 μm
between the coating roller system and the substrate surface a primary
layer was applied on one side of a boro-float glass substrate. The
primary layer was pre-cured under a UV lamp for 10 seconds (s). A
silicone stamp die (PDMS) with micro-lens structure was applied onto the
primary layer which still was in a malleable condition and subsequently
said layer was hardened with the help of the UV lamp straight through the
stamp die (exposure time: 5 min). After the removal of the stamp die the
structure of the stamp die had been transferred into the primary layer.
The final layer thickness of the first layer was about 25 μm.

[0148] After UV curing the sol-gel layer had a modulus of elasticity of
800 N/mm2 +/-10% and after thermal curing at 200° C. for 1
hour (h) the modulus of elasticity was 2,000 N/mm2 +/-10%.

EXAMPLE 2

[0149] During Example 2, 0.06 mol of GPTES
(glycidoxypropyltriethoxysilane) and 0.02 mol of TEOS (tetraethoxysilane)
and 0.01 mol of MTEOS (methylthethoxysilane) and 0.01 DMDEOS
(dimethyldiethoxysilane) were added into a vessel and hydrolyzed with 2.3
g of water in which 0.344 g of PTSH (para-toluene sulfonic acid) had been
solved. After stirring for three hours the volatile reaction products
generated were removed from the mixture with a rotary evaporator.

[0150] To 10 g of the hydrolyzate 8.5 g of a solution of 50% of a
phenylpolysiloxane resin in ethanol were added.

[0151] Finally, 3 g of a solution of 20% of the cationic photoinitiator
Irgacure® 250 in 1-methoxy-2-propanol were added to the coating
composition. Subsequently, the volatile solvent was removed with a rotary
evaporator at 80° C. and 100 mbar.

[0152] By means of screen printing using a 34 screen a primary layer
having a thickness of about 40 μm was applied onto a soda-lime glass
substrate. Subsequently, this layer was allowed to stand for 2 h at room
temperature.

[0153] After the evaporation of the solvent the remaining primary layer
was pre-cured under a UV lamp for 10 s. Subsequently, a structured
silicone stamp die (PDMS) with a light guide structure was applied onto
the primary layer which still was in wet condition and the layer was
hardened with the help of the UV lamp straight through the stamp die
(exposure time: 5 min). After the removal of the stamp die the structure
of the stamp die had been transferred into the primary layer. The final
layer thickness of the first layer was about 30 μm.

[0154] After UV curing the sol-gel layer had a modulus of elasticity of
1,200 N/mm2 +/-10% and after thermal curing at 240° C. for 1
h the modulus of elasticity was 2,500 N/mm2+/-10%

EXAMPLE 3

[0155] During Example 3, 0.06 mol of GPTES
(glycidoxypropyltriethoxysilane) and 0.02 mol of TEOS (tetraethoxysilane)
and 0.01 mol of MTEOS (methyltriethoxysilane) and 0.01 DPDEOS
(diphenyldiethoxysilane) were added into a vessel and hydrolyzed with 2.3
g of water in which 0.344 g of PTSH (para-toluene sulfonic acid) had been
solved. After stirring for three hours the volatile reaction products
generated were removed from the mixture with a rotary evaporator.

[0156] To 10 g of the hydrolyzate 8.5 g of a solution of 50% of a
polysiloxane resin having a ratio of phenyl to methyl of 1.3/1, a
molecular mass of 2,000 to 4,000, a content of SiO2 of about 52% and
a content of silanol groups of 6% by weight in butanol were added.

[0157] Finally, 3 g of a solution of 20% of the cationic photoinitiator
Irgacure® 250 in 1-methoxy-2-propanol were added to the coating
composition. Subsequently, the volatile solvent was removed with a rotary
evaporator at 80° C. and 100 mbar.

[0158] By means of roll coating a primary layer having a thickness of
about 150 μm was applied onto a soda-lime glass substrate.
Subsequently, this layer was allowed to stand for 2 h at room
temperature.

[0159] After the evaporation of the solvent the remaining primary layer
was pre-cured under a UV lamp for 10 s. Subsequently, a structured
silicone stamp die (PDMS) with a light guide structure was applied onto
the primary layer which still was in wet condition and the layer was
hardened with the help of the UV lamp straight through the stamp die
(exposure time: 5 min). After the removal of the stamp die the structure
of the stamp die had been transferred into the obtained sol-gel layer.
The final layer thickness of the cured lacquer was about 60 μm.

[0160] After thermal curing at 230° C. for 1 h the modulus of
elasticity of the sol-gel layer was 2,600 N/mm2+/-10%.

EXAMPLE 4

[0161] During Example 4, 0.08 mol of MPTES
(methacryloxypropyltriethoxysilane) and 0.02 mol of TEOS
(tetraethoxysilane) were added into a vessel and hydrolyzed with 1.44 g
of water in which 0.344 g of PTSH (para-toluene sulfonic acid) had been
solved. After stirring for three hours the volatile reaction products
generated were removed from the mixture with a rotary evaporator.

[0162] To 10 g of the hydrolyzate 6.0 g of a solution of 75% of a
polyester-modified polysiloxane in methoxypropylacetate and isopropanol
were added. Finally, 1 g of the radical photoinitiator Irgacure® 819
was added to the coating composition.

[0163] By means of screen printing using a 54 screen a primary layer
having a thickness of about 20 μm was applied onto a soda-lime glass
substrate. Subsequently, this layer was dried for 1 h at about 60°
C. by means of an IR lamp.

[0164] Subsequently, a structured silicone stamp die (PDMS) with an
optical lens structure was applied onto the primary layer which still was
in wet condition and the layer was hardened with the help of the UV lamp
straight through the stamp die (exposure time: 2 min). After the removal
of the stamp die the structure of the stamp die had been transferred into
the obtained sol-gel layer. The final layer thickness of the cured
lacquer was about 10 μm.

[0165] After UV curing the modulus of elasticity of the sol-gel layer was
3,360 N/mm2 +/-10% and after thermal curing at 280° C. for
0.2 h the modulus of elasticity was 4,200 N/mm2+/-10%.

EXAMPLE 5

[0166] During Example 5, 0.08 mol of MPTES
(methacryloxypropyltriethoxysilane) and 0.018 mol of TEOS
(tetraethoxysilane) were added into a vessel and hydrolyzed with 1.15 g
of water in which 0.21 of PTSH (para-toluene sulfonic acid) had been
solved. After stirring for three hours the volatile reaction products
generated were removed from the mixture with a rotary evaporator.

[0167] Then, to 10 g of the hydrolyzate 15 g of a solution of 75% of a
polyester-modified polysiloxane in methoxypropylacetate and isopropanol
were added. Subsequently, to that were added 30 g of a solution of 20% by
weight of highly refractive nanoparticles (TiO2, anatase, 16 nm) in
propanol.

[0168] Finally, 1 g of the radical photoinitiator Irgacure® 819 was
added to the coating composition. Subsequently, the volatile solvent was
removed at RT and 30 mbar with a rotary evaporator.

[0169] By means of screen printing a primary layer having a thickness of
about 40 μm was applied onto a soda-lime glass substrate.
Subsequently, this layer was dried for 1 min at 60° C. by means of
an IR lamp.

[0170] Subsequently, a structured silicone stamp die (PDMS) with an
optical line grid structure was applied onto the primary layer which
still was in wet condition and the layer was hardened with the help of a
UV lamp straight through the stamp die (exposure time: 4 min). After the
removal of the stamp die the structure of the stamp die had been
transferred into the obtained sol-gel layer. The final layer thickness of
the cured lacquer was about 20 μm and the refractive index of the
lacquer was about 1.6.

[0171] After UV curing the modulus of elasticity of the sol-gel layer was
2,100 N/mm2 +/-10% and after thermal curing at 270° C. for
0.2 h the modulus of elasticity was 2,800 N/mm2+/-10%.

EXAMPLE 6

[0172] During Example, 6, 0.08 mol of MPTES
(methacryloxypropyltriethoxysilane) and 0.018 mol of TEOS
(tetraethoxysilane) were added into a vessel and hydrolyzed with 2.3 g of
water in which 0.21 g of PTSH (para-toluene sulfonic acid) had been
solved. After stirring for three hours the volatile reaction products
generated were removed from the mixture with a rotary evaporator.

[0173] To 10 g of the hydrolyzate 5.0 g of a solution of 75% of a
polyester-modified polysiloxane in a mixture of methoxypropylacetate and
isopropanol and 0.5 g of glycerol-1,3-dimethacrylate urethane
triethoxysilane were added. Finally, 1 g of the radical photoinitiator
Irgacure® 819 was added to the coating composition.

[0174] By means of screen printing using a 54 screen a primary layer
having a thickness of about 20 μm was applied onto a soda-lime glass
substrate. Subsequently, this layer was dried for 1 min at about
60° C. by means of an IR lamp.

[0175] Subsequently, a structured silicone stamp die (PDMS) with an
optical lens structure was applied onto the primary layer which still was
in wet condition and the layer was hardened with the help of the UV lamp
straight through the stamp die (exposure time: 2 min). After the removal
of the stamp die the structure of the stamp die had been transferred into
the obtained sol-gel layer. The mean final layer thickness of the cured
lacquer was about 14 μm.

[0176] After UV curing the modulus of elasticity of the sol-gel layer was
3,500 N/mm2 +/-10% and after thermal curing at 280° C. for
0.2 h the modulus of elasticity was 4,800 N/mm2+/-10%.